The present invention relates to an impurity detecting apparatus for efficiently detecting various foreign substances or impurities in a material and a detecting method therefore.
Tobacco leaves, a harvest, are packed in various forms as they are carried into tobacco material plants or cigarette manufacturing plants. After they are unpacked in these plants, the tobacco leaves are separated according to their varieties or mixed with other varieties. In this state, they are transported as the material for cigarettes to the next stage.
In some cases, materials in a transportation process may be mixed with some foreign substances, such as wrappers or strings used to pack tobacco leaves or some pieces of moisture-proof paper used to line packages. These foreign substances or impurities must be removed in the material transportation process. To attain this, the impurities should be detected during the material transportation. If the impurities include any plastic materials that produce poisonous gases as they burn, in particular, they must be securely detected and removed.
Conventionally, a detecting apparatus with a video camera is used to detect impurities. According to this detecting apparatus, the video camera shoots the material being transported, and a decision circuit of the apparatus then detects impurities in the material according to image data obtained by the shooting. More specifically, the decision circuit detects the impurities in the materials in accordance with differences in color between tobacco leaves and the impurities.
The detecting apparatus described above can be effectively used only in the case where the colors of the impurities to be detected differ substantially from those of the tobacco leaves. If the impurities have the same or similar colors as the tobacco leaves, therefore, they cannot be detected practically.
If the tobacco leaves are of a same variety, moreover, they have their respective colors, which substantially vary depending on the quality of the leaves. In the case where the material include tobacco leaves of different varieties, in particular, therefore, it is very hard to detect impurities in them.
The object of the present invention is to provide a detecting apparatus and a method capable of accurately detecting impurities in a material without regard to differences in color between the material consisting of tobacco leaves and a plurality of kinds of impurities.
A detecting apparatus of the present invention comprises an illuminating device for applying detection light to a material when the material is transported, a light receiving device for receiving the detection light reflected by the material, a plurality of light receiving devices being capable of outputting respective reflection intensities of a plurality of specific wavelength components of the detection light, where the specific wavelength components have different reflection intensities, respectively, between the material and impurities, and decision circuit for comparing the respective reference reflection intensities of the specific wavelength components inherent in the material and the reflection intensities delivered from the plurality of light receiving devices and detecting the impurities in the material according to the result of the comparison.
The principle of detection of impurities according to the present invention is based on definite differences in reflection intensity for the specific wavelength components of the detection light between the material and the impurities, obtained when the detection light is applied to the material and the impurities and the reflectance or reflection intensity of the detection light reflected by the material and the impurities is measured.
If the material and the impurities have the same color, therefore, the impurities in the material can be detected by comparing the respective reference reflection intensities of the specification wavelength components inherent in the material and the respective reflection intensities of the measured specific wavelength components, with respect to the specific wavelength components of the detection light.
Infrared rays or laser beams may be used as the detection light.
In the case where the illuminating device of the detecting apparatus includes a source of generation for generating infrared rays, each light receiving device includes extracting means for extracting the specific wavelength components of the infrared rays reflected by the material, and outputs the respective reflection intensities of the extracted specific wavelength components.
More specifically, the illuminating device may further include a rotatable polygon mirror, the polygon mirror being capable of reflecting the infrared rays from the source of generation onto the material on the conveyor and scanning the material on the conveyor with the reflected infrared rays in the transverse direction of the conveyor. Preferably, the polygon mirror transmits the reflected infrared rays to the light receiving device. In this case, a compact detecting apparatus can be provided.
It is desirable that the light receiving device outputs reflection intensities of at least three specific wavelength components of the detection light.
The light receiving device may include an infrared camera having a range that covers an entire transportation width of the material. In this case, the infrared camera includes dividing means for dividing received reflected infrared rays into a plurality of separate beams of infrared rays, a plurality of band-pass filters for extracting specific wavelength components from the separate beams, respectively, said specific wavelength components differing from each other and a plurality of infrared line scanners for receiving the specific wavelength components extracted by the band-pass filters and outputting reflection intensity distributions of the received specific wavelength components, respectively.
The illuminating device of the detecting apparatus can apply only the specific wavelength components of the detection light to the material. For example, the illuminating device includes a source of generation for generating infrared rays as the detection light and extracting means for extracting the specific wavelength components from the source of generation, and the illuminating device applies only the extracted specific wavelength components to the material on the conveyor.
In the case where infrared rays are used as the detection light, the infrared rays heat the material. In the case where only the specific wavelength components of the infrared rays are applied to the material, however, the material receives little thermal energy, so that the material can be prevented from overheating. In consequence, there is no possibility of the material drying excessively during the detection of the impurities, so that the quality of the material can be maintained.
Preferably, the illuminating device further includes cooling means for cooling the source of generation of the infrared rays. In this case, heat release from the illuminating device can be reduced.
The detecting method of the present invention is carried out using the detecting apparatus described above.